A similar screw compressor is generally known, e.g., from the British Pat. No. 1358505. In these known screw compressors the bearing devices for the rotors consist of lubricated roller bearings. In this context the properties of the lubricant are very important.
A problem with these known screw compressors is that the lubricant or the bearings is often contaminated by the medium to be compressed, causing the lubricating properties of the lubricant to deteriorate. This may result in an unacceptably short life of the bearings, the appearance of vibrations and of excessive noise of the compressor. When the compressor is applied in cooling systems, for example, a cold start of the compressor may suck in liquid coolant which may mix with or dissolve in the lubricant in the crankcase of the compressor. In other systems, too, similar problems may occur due to the effect of the medium to be compressed on the lubricant.